Clean the cabbage, wash it and let it crisp in ice water for about 30 minutes in the refrigerator. Drain the cabbage, cut into quarters and cut out the stalk. Cut cabbage into fine strips. Peel, wash and roughly grate the carrots.
Peel and finely grate the onion. Mix cabbage and carrots. Stir sour cream, sugar, vinegar, onion and mayonnaise until smooth. Season with salt and pepper. Mix the marinade with the cabbage and leave to stand for an hour.
Season salad again and serve.